The present inventors have proposed, by JPA-2000-262632, a stent graft indwelling device having a catheter, a pushing rod (also called “dilator”) and a sheath, in which a swollen portion that has the form, for example, of an ellipsoid, for blocking or sealing a leading end of the sheath is provided in the vicinity of the leading end of the catheter and the swollen portion is provided with an engagement means such as a notch or the like so that a hook attached to the leading end of a stent unit can be removably engaged therewith.
In JP-A-2000-350785, further, the present inventors have proposed a stent graft indwelling device having a dilator composed of a base body portion, a stent graft holding portion and a head portion and a sheath loadable with the dilator, in which the head portion is shaped in the form of a semi-ellipsoid or a semi-sphere and is partly projected from the leading end of the sheath for blocking or sealing the leading end of the sheath, that part of the head portion inside the sheath is provided with an engagement means such as a notch or the like such that a hook attached to the stent is removably engaged therewith and one or a plurality of contrast medium delivery channel(s) and a guide wire guiding channel are provided in the above dilator.
The above proposed stent graft indwelling devices have the following novel features.
That is, (a) it is ensured that safe and reliable indwelling of the stent graft is made even in an intracorporeal organ such as an extremely curved blood vessel, etc., and reducing the pains and burdens of a patient. (b) The entering of a body fluid such as arterial blood into a stent graft portion held in the sheath can be prevented, and the stent graft held in the sheath can be safely delivered into an intracorporeal tubular member such as a blood vessel (artery) without damaging the inner wall thereof. (c) When the catheter is inserted into an intracorporeal tubular member such as blood vessel while a contrast medium is ejected from a contrast medium ejecting port, the insertion site of the catheter can be monitored by image, and when the catheter is moved forward and backward while the contrast medium is ejected from the contrast medium ejecting port, thereby enabling a image-wise spotting of a safety site in a diseased part of the intracorporeal tubular member such as a blood vessel in a short period of time. Therefore, the insertion of the stent graft housed in the sheath into the intracorporeal tubular member such as a blood vessel and the determining of indwelling position of the stent graft are safe and easy. (d) When the stent graft is pushed out of the sheath and self-dilated in a pre-determined indwelling or placement position in an intracorporeal tubular member such as a blood vessel, the shifting of the stent graft caused by the pressure of a body fluid such as a blood flow is prevented. (e) The stent graft can be broadened in application to the treatment of aneurysm, etc., to which no conventional stent grafts have ever been applied, thereby a beneficial treatment method for many patients with aneurysm, etc., can be provided. (f) The stent graft is also provided with effects that ensure direction of the curvature-based stent graft design and the like.
These stent graft indwelling devices that have been proposed have the above excellent features and produce remarkable advantageous effects as compared with conventional devices.
However, unfortunately, these stent graft indwelling devices have a so-called one-piece structure in which the dilator is formed integrally with its head portion (called a swollen portion or fixed chip portion as well) of the dilator. Thereafter, the present inventors have found it desirable to ensure that the stent graft does not rotate in the sheath, that it does not move forward or backward and that it does not come off the dirator when it is housed in the sheath. Further, it has been found that when the stent graft is to be released from the sheath, it is desirable that the stent graft should come off easily and without any resistance. However, it is difficult to overcome these problems with the structure of the above-described dilator head.
Further, the dilator has the head portion whose swollen portion has a greatly expanded form like a spindle as compared with a holding portion (for example, see FIG. 2 of JP-A-2000-350785), so that it has been not easy to process a metal mold for integrally molding the dilator with an injection machine or the like. In actual medical care facilities, therefore, a craft man produces each dilator with swollen portion by piece by piece cutting work followed by thermal processing, etc., and the production thereof takes time. It has been also found that products vary in form.
The following problems have been also found. In the above stent graft indwelling device, the form of the above swollen portion of the dilator is fixed, so that it is not always possible that the sheath be inserted at a constant angle to the form of a blood vessel when inserting the sheath. And hence the stent graft is released into a blood vessel while it is dilated unit by unit, so that it is difficult to finely or precisely adjust the exact position and fixing angle of the above stent graft. Further, the blood vessel size and the degree of curvature thereof differ depending upon individual patients, and when these stent graft indwelling devices are used for a patient having an extremely or excessively curved blood vessel or for a patient having a boss in the distal arc portion of a thoracic aorta, it has not been necessarily easy to safely place the released stent graft.
That is because, when the stent graft is to be placed or in the center (heart) side rather than in a nutrient canal branch portion of a captu-cervical part in the arc portion of an aorta, it is the most important object to make sure that the contact of the stent graft base body and the leading end of the sheath to the greater curvature side of the arc portion of the thoracic aorta be minimized for preventing complications such as cerebral infarction.
In view of the importance of the problems associated with conventional stents, the present inventors have made diligent studies for providing a stent that is remarkably improved in safety and a tracking property during its delivery in the artery and in long-term stable indwelling in a diseased part, and have arrived at this invention.